Standard power supplies cause hurdles for designers, as they force them to work with predetermined power specifications. Configurable power supplies, like Mean Well’s NMP and UMP-400 series, help overcome these limitations.

Configurable power supplies provide designers flexibility by offering programmable outputs through their front end modules that provide DC-DC regulation. “The front end is connected to the modules by either quick connect or plug-and-play style. The power modules can be used to create simple and compact distributed power supply systems,” Engineering.com notes.

Figure 1. A traditional configuration with multiple AC-DC power supplies (left) versus a distributed system with configurable power supplies (right).

“We provide different flavors of output modules that are compatible with the front end supplier, so the users can just mix and match what they need in terms of output-voltage, output-power levels, etc.,” Kai Li, Project manager at Mean Well told Engineering,com. “Sophisticated machinery requires multiple output voltage levels. A 3D printer, for example, would need 24V to drive the motor, 12V to drive the display panels and 3.3V to control some wireless features. With a configurable power supply, I just need a single unit to support all of those different voltages.”

The NMP-650 (650W) and NMP1K2 (1,200W) are 1U low profile configurable power supplies that include four adjustable output modules that cover ranges from 3V to 55V. NMP series also offer intelligent control functions.

“It enables intelligent controls from its various control signals. We can remotely turn the unit on and off, and we can do that with a global control signal to the front end, or we can do it locally at each of the output modules,” Li explained.

Beyond the flexibility and control features, Mean Well NMP Series benefits include:.

• Low Current Leakage - damaged grounding connections can cause both AC and DC leakage current which can flow to ground via anything conductive including a human body. This dictates that designers must limit this current value. Standard power supplies can only loosely control leakage current which creates issues in meeting specific appliance requirements.

Configurable power supplies offer a lower current leakage and are designed and certified as a whole unit considering all leakage current performance.

The Mean Well NMP supplies have Earth leakage current <400uA/264VAC and Touch current <100uA/264VAC

• Electromagnetic Compatibility Performance (EMC) - power supplies can generate electromagnetic interference (EMI) that impact nearby devices which is higher in standard power supplies. EMC is the ability to maintain performance in spite of EMI and not generating its own. If an electrical system uses EMI can increase. A single configurable power supply can lower the effect and  engineers do not have to EMI debug, the most time-consuming part of designing electromechanical products. They can also limit the call for additional filters and design corrections.

• High Power Density - given the ever-increasing demand for smaller power supplies with the same, or higher power, power density issues efficient cooling is required.The NMP power supplies attain up to 91 percent efficiency using this. The NMP-650 (650W output power) has one built-in cooling fan and the NMP-1K2 (1,200W) has two..

“When we were designing the [NMP], we had to very carefully consider the aerodynamics, the air flow of the fans and how the airflow interacts with the components,” he said. “So it's overall a combined design experience from Mean Well's over 35 years of designing switching power supplies.”

Functions of Configurable Power Supplies

The Mean Well NMP series has added functions that improve the flexibility of their supplies. 

• An active power factor correction (PFC) function - this protects any designed devices while improving conversion efficiency. Active current sharing and parallel control capabilities allow users to increase the total output current by connecting up to four (NMP650) or six (NMP1K2) modules of the same output voltage rating (meaning the difference in voltage should be less than 0.2V).

• Higher output voltages - this Mean Well achieves by connecting output modules in series (where the total output current should not exceed the current rating of the lowest rated module connected in series).

Figure 2. Parallel connection of six NMS240 modules. (Image courtesy of Mean Well .)

The output voltage of the modules can be adjusted via the step voltage regulator (SVR), which is trimmed by turning the VR60 potentiometer near the output terminals. Turning the VR60 clockwise increases the voltage, and turning it counter-clockwise reduces the voltage. The output voltage is programmable in the range of  3 – 6V (NMS-240-05), 6 – 15V (NMS-240-05), 15 – 30V (NMS-240-24), and 30 – 55V (NMS-240-48). Additionally, the voltage and current can be trimmed to 40 – 100 percent of the rated values by applying external DC voltages (see graph below).

Figure 3. Output current can be adjusted by applying an external DC voltage. (Image courtesy of MEAN WELL.)

“We only have four different modules, with the nominal voltages of 5V, 12V,  24V and 48V,” Li explained. “Each module has a very wide adjustment range. Some of our competitors make over one hundred different modules. Our users do not have to go through many pages of spec sheets just to find the right module.”

The built-in remote sense output module in the NMP series can compensate for voltage drops up to 0.5V. Twisting or shielding the voltage sense wires prevents external noise interference. The status of the power supply is monitored by the DC OK signal output, when operating properly, the DC-OK signal is HIGH (4.5~5.5V) and the LED indicator is lit.

The NMP output modules have built-in current protections that activate when the output is short-circuited or the output current exceeds 115% ± 10% of the rated output current. Each output module also has built-in over-voltage protection. Once the protection is triggered, the units shut off for 10 seconds before re-cycling AC power to power on the unit. There is also a built-in fan-lock protection circuit. The NMP modules’ output shuts off when the DC fan stops operating (in case of fan-lock, loose connectors or broken wires). It is necessary to turn off the AC power and remove the conditions causing the fan-lock.

If the internal temperature exceeds a pre-set value the NMP system built-in thermal detection circuit will send a HIGH signal. The output shuts down automatically if the internal temperature continues to increase and exceeds the “safe limit” value. This signal is LOW when the internal temperature is within a normal value.

Power Supply Safety

Power supply safety is a critical factor and the NMP series complies with regulations including the medical 2x Means Of Patient Protection (MOPP) and ITE standards.

MOPP is the standard of basic safety required for medical electrical equipment and regulates the isolation level of the power supplies. The IEC/EN 60601-1, administers electrical safety for medical devices  with detailed measures to guard against electric shock.

There are two MOP protections: MOOP and MOPP. MOOP stands for Means Of Operator Protection, and it is meant for devices that will not come into contact with the patient. MOOP typically has a lower level of isolation and leakage requirements, mainly dictating the isolation level of the units of the power supplies.

“Another key feature [of NMP] is that both medical and the ITE [Information Technology Equipment] safety standards are approved,” Li said. “So customers can use this for industrial applications, such as 3D printers, and also for medical machines like imaging or surgical machines.”

The Fanless Mean Well UMP-400

Mean Well’s other configurable power supply, the UMP-400  can operate as an independent 400W (24V or 48V) single output power supply. The UMP-400 is a completely configurable fanless power supply; no forced airflow is required to cool the unit. This makes it a noiseless device and very popular for noise-sensitive environments such as hospitals or shopping centers.

Figure 4. A MEAN WELL UMP-400 power supply. (Image courtesy of MEAN WELL.)

The UMP-400 is configurable into a multi-channel modular power supply by incorporating the NID series non-isolated DC-DC converters. With output power up to 100W adjustable for common voltages of 5V, 12V, 15V and 24V, the UMP-400 is certified to ITE 62368-1 safety standards and designed to meet 2x MOPP safety standards.

Eliminating the fan from a power supply can improve its reliability, reduce system design cost, and eliminate acoustic noise. The Mean Well UMP-400 avoids issues with fan failures and reduces maintenance costs. The company recommends the UMP-400 for applications including diagnostic or biological facilities, test or measurement systems, telecommunication equipment, industrial automation machinery, industrial control systems and mechanical and electrical equipment.

To learn more about the benefits of configurable power supplies, visit onlinecomponents.com for more information on the Mean Well NMP-1K2, NMP-650, and UMP-400.